As fossil fuels are exhausting, various alternative energy sources, for example, hydroelectric power, wind electric power, geothermal electric power or solar electric power, are actively developed all over the world. Among these alternative energy sources, solar electric power are widely used, for example, in public constructions, including traffic signs such as speed limit signs, slogan signs or road margin signs, wherein the road margin signs usually comprises plural underground lights disposed at intervals. In the earlier times, in order to make drivers easier to see non-illuminating road margin signs, plural Cat's Eye Stones, which can reflex light, were disposed at intervals along the road margin. However, Cat's Eye Stones reflex light when irradiated by light, but they themselves do not emit light; therefore, in case that drivers do not turn on head lights or in case that drivers drive through a foggy area, the drivers may be still exposed to danger due to poor light reflex of Cat's Eye Stones.
In order to overcome the disadvantages of Cat's Eye Stones, some self-illuminating underground lights were developed. Such underground light usually comprises a solar panel, a circuit board, a rechargeable battery and a light-emitting diode, which are all encased in a transparent body. The conventional transparent body consists of at least two semi-housings. On assembling, all electronic elements are first placed into one semi-housing, then covered with the other semi-housing and sealed. However, when subjected to sun shining and rain leaching in external environment for long period, the sealing of the conventional transparent body may be damaged, and moisture and contaminants from environment may penetrate through the sealing and enter into the transparent body, which may lead to damage of the electronic elements encased therein and shortening of the life span of the underground light. In addition, the conventional transparent body is usually made of glass, or injection-molded polycarbonate (PC), which may deteriorate or become yellow or brittle if subjected to sun shining and rain leaching in external environment for long period; as a result, the electronic elements encased therein may be exposed to the danger of being damaged by external environment and the life span of the underground light may be shortened.
Therefore, it is desired to development a self-illuminating lamp, which can segregate the electronic elements from external environment and is durable in use.